The United States, which bans Iranians from entering, should not pretend that it cares about their plight now, charged an Iranian Foreign Ministry spokesman on Saturday, in response to a warning from U.S. President Donald Trump over protests across Iran.

"The Iranian people will not pay any heed to these worthless and opportunistic remarks from the United States," said foreign ministry spokesman Bahram Ghassemi.

Reports of anti-government protests in at least six Iranian cities on Friday prompted Trump to warn Tehran that "The world is watching!"

"Many reports of peaceful protests by Iranian citizens fed up with regime's corruption & its squandering of the nation's wealth to fund terrorism abroad," Trump wrote on Twitter.

"Iranian govt should respect their people's rights, including right to express themselves," he continued.

Ghassemi added on Saturday that there are democratic channels in Iran over which the people can legitimately air their demands.

A state television report on Saturday quoted Ghasemi, as saying that "Iranian people give no credit to the deceitful and opportunist remarks of U.S. officials or Mr. Trump."

"The Iranian people see no value in the opportunistic remarks by American officials and Mr Trump," Bahram Ghasemi also said on its website.

He said Iranians remembered Trump's actions in barring them from entry to the United States and "the arrest of many Iranians in that country on baseless pretexts".

According to local reports, thousands had taken to the streets to air their grievances - including the high cost of living, unemployment and Tehran's Middle East policies - for a second day on Friday, despite warnings from security officials and arrests the day before.

Videos on social media showed protesters chanting slogans against the country's governing clerics including "Shame on you mullahs, leave our country in peace." It was not possible to verify the videos.

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